Rename labelWidth/Height to tickWidth/Height.
Minor reordering of axis options.
Added axis.tickFont as an override for axis.font.
Updated axis option defaults and documentation.

Updated the axis option defaults and docs for tickColor, tickFont,
tickWidth, and tickHeight. Also re-organized the API docs to match the
master list, and revised many areas for clarity.
Inline legacyStyles; it wasn't reused anyway.
Axes can now have basic horizontal text labels.

Labels are provided via a 'label' option on the axis, and can be styled
with the flot-axis-label class.  The labelFont option works similarly to
tickFont, as an override for the default font or the flot-axis-label
class.  The labelPadding option adds extra space between the axis and
its label.

Since most plots with axis labels currently use @markrcote's
flot-axislabels plugin, we also support the axisLabel and
axisLabelPadding options, and the axisLabels / axis[name]Label CSS
classes, to make it as easy as possible to transition from that plugin.
These are deprecated, and will be removed in 1.0.

The implementation uses the internal text API introduced in 0.8.